Highly adaptive recording method and optical recording apparatus

ABSTRACT

An optical disk recording method includes the steps of: providing a multi-pulse chain from a recording wave; independently changing the pulse rise timing and pulse fall timing (pulse width) of the first pulse in the multi-pulse chain in accordance with a preceding space length and a recording mark length; changing the pulse rise timing and pulse fall timing (pulse width) in accordance with a following space length and the recording mark length in a predetermined timing or in independence; and in relation to the smallest mark recorded by irradiation with mono pulse, changing the rise timing in accordance with the preceding space length and the recording mark length and the fall timing (pulse width) in accordance with the following space length and recording mark length, compensating various optical disks different in recording material without change of the fundamental waveform.

INCORPORATION BY REFERENCE

This application is a Continuation of U.S. application Ser. No.10/919,489, filed Aug. 17, 2004 claiming priority of JapaneseApplication No. 2003-322426, filed Sep. 16, 2003, the entire contents ofeach of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical disk for recordinginformation by energy beam irradiation and particularly to an opticaldisk recording method having an excellent effect on various high-densityrecordable optical disks different in composition and recordingmechanism, and an optical disk device using the recording method.

2. Description of the Related Art

A DVD-RAM using a phase change material for achieving a recordingcapacity of 4.7 GB per surface of a 120 mm-diameter disk has been putinto practice in recent years. In the DVD-RAM, a recording film isprovided with a first state (mark) and a second state (space). Apredetermined repetitive pattern of the first state and the second stateis formed to perform mark edge recording of information. A way ofchanging the level of irradiation power with the passage of time in thecase where an energy beam is applied on the recording film to recordinformation in the recording film is generally called recordingstrategy.

The recording strategy of the DVD-RAM is as shown in FIG. 2. The energybeam is pulsated so that the level of the energy beam changes among afirst power level (recording power level Pw) for obtaining the firststate, a second power level (bias power level Pb2) for obtaining thesecond state and a third power level (bias power level Pb1) lower thanthe first and second power levels. Particularly when a recording mark asthe first state needs to be formed, the recording film is irradiatedwith a multi-pulse chain having light pulses of the first power leveland light pulses of the third power level arranged alternately inaccordance with the length of the recording mark in order to prevent therecording mark from being distorted geometrically.

Incidentally, if the distance between positions irradiated with tworecording pulses adjacent to each other is relatively small comparedwith the light spot size of the energy beam applied on the recordingfilm, there is a high possibility that both geometrical mark distortionand mark edge shift will occur because the light intensity distributionsof the two recording pulses overlap each other. If the mark or space istoo short, there is a high possibility that mark edge shift will occurin the waveform of a playback signal because the mark or space cannot bediscriminated sufficiently on the basis of a playback light spot.

To solve the problem of mark edge shift, a correction technique has beendisclosed and put into practice (e.g. see U.S. Pat. No. 5,490,126). Inthe correction technique, the aforementioned recording strategy based ona multi-pulse chain is used so that a light pulse of the first powerlevel having a predetermined pulse width is applied particularly on eachof leading and trailing portions of each mark, and that recording isperformed while the positions of the leading and trailing portions ofthe mark are changed at any time in accordance with the respectivelengths of the mark and preamble and following spaces to be recorded.

The way of generating the mark edge shift largely depends on the designof the recording film. A recording strategy adapted to a specificrecording film is not always adapted to another recording film.Therefore, a correction technique using the recording strategy based ona multi-pulse chain has been disclosed and put into practice to copewith various recording films (U.S. Pat. No. 6,160,784). That is, onecase is selected, in accordance with the disk, from a first case wherethe pulse rise timing of the first pulse applied on the leading portionof each mark is changed at any time in accordance with the recordingmark length and preceding space length while the pulse fall timing ofthe first pulse is fixed and a second case where the pulse rise timingof the first pulse and the pulse fall timing of the first pulse arechanged at any time in accordance with the recording mark length andpreceding space length while the width of the first pulse is fixed. Thelast pulse applied on the trailing portion of each mark is generated inthe same manner as the first pulse. That is, one case is selected, inaccordance with the disk, from a first case where the pulse fall timingof the last pulse is changed at any time in accordance with therecording mark length and following space length while the pulse risetiming of the last pulse is fixed and a second case where the pulse risetiming of the last pulse and the pulse fall timing of the last pulse arechanged at any time in accordance with the recording mark length andfollowing space length while the width of the last pulse is fixed.

The density of an optical disk has kept on increasing recently with theadvance of increase in quantity of data to be used. A DVD having acapacity of about 4.7 GB (gigabytes), inclusive of the aforementionedDVD-RAM, has generally come into wide use as against a CD having acapacity of about 700 MB (megabytes). A next-generation optical diskhaving a large capacity of 20 GB or more capable of recordinghigh-definition images for 2 hours has been further developed andcommercialized. In the next-generation optical disk, a semiconductorlaser with a short wavelength band of 405 nm (blue violet) is used as alight source and the numerical aperture of an objective lens is improvedto 0.85. Moreover, the modulation code is changed from EFM-plus used inthe DVD to 1-7 PP modulation. In expression in run length limited code,the modulation code used in the next-generation disk is RLL(1, 7)whereas the modulation code used in the DVD is RLL(2, 10). According tothe change of the modulation code, the range of change of the mark/spacelength used in the next-generation disk is from 2Tw to 8Tw whereas therange of change of the mark/space length used in the DVD is from 3Tw to11Tw when Tw is the width of a data detection window.

FIG. 5 shows various characteristics in each code in the case where thetransfer time T is 24 ns per user bit. Since the smallest mark/spacelength has a tendency toward decreasing though the detection windowwidth has a tendency toward increasing, there is a problem that thenext-generation optical disk is different from the DVD-RAM in powerlevels and recording strategy necessary for recording an optimum mark.Moreover, since the smallest mark/space length is reduced relative to aplayback light spot, there is a problem that mark edge shift becomesmore remarkable because of reduction in resolving power.

The smallest mark length in a linear direction in the next-generationoptical disk is 0.08 μm whereas the smallest mark length in a lineardirection in the DVD-RAM is 0.28 μm. The next-generation optical diskhas a structure in which adjacent marks/spaces are closer to each otherphysically. For this reason, there is a problem that thermalinterference is easily caused by energy injected at the time ofrecording a mark. Particularly when a high-speed recordable recordingmedium will appear in the future, it is preferable that the recordingmedium can be used in a low-speed recording apparatus in terms ofdownward compatibility. It may be foreseen that the problem of thermalinterference will become more serious because the high-speed recordablerecording medium must have heat storage characteristic as a result ofimprovement in recording sensitivity. For this reason, there is aproblem that mark edge shift at the time of recording becomes moreremarkable.

SUMMARY OF THE INVENTION

It may be foreseen that higher accuracy than that in the conventionaltechnique is required of the next-generation optical disk with respectto correction of mark edge shift.

It may be conceived that another material such as an organic coloringmaterial used in a DVD-R than the phase change film used in the DVD-RAMis used as a recording medium in the next-generation optical disk. Whenthe material of the recording film is changed, the mark-formingmechanism per se may be changed. It is however preferable that recordingstrategy can be adapted to various recording media when only numericalvalues of parameters are changed without use of recording waveformsdifferent in accordance with the media, that is, without any change of afundamental waveform. As for the aforementioned high-speed recordablemedium, it is preferable that recording strategy can be adapted to themedium when only numerical values of parameters are changed without anychange of the fundamental waveform between a high-speed recording modeand a low-speed recording mode. This is essential particularly to thecase where data are recorded in the disk at a constant angular velocity(CAV).

In consideration of the aforementioned circumstances, an object of theinvention is to provide an optical disk recording method and an opticaldisk device in which: a modulation code mark having a minimum mark/spacelength small relative to the width of a detection window can be recordedaccurately on various recording media different in recording filmmaterial or recording mechanism and high-speed recordable media whichwill appear in the future when only numerical values of parameters arechanged without any change of a fundamental waveform configuration; andit is possible to compensate particularly for mark edge shift caused bythermal interference at the time of recording and for mark edge shiftcaused by resolving power at the time of reproducing. Another object ofthe invention is to provide an optical disk which makes it easy tooperate the optical disk recording method and the optical disk device.

To solve the aforementioned problem, the optical disk recording method,the optical disk device and the optical disk according to the inventionare configured as follows.

There is provided an optical disk recording method used for an opticaldisk having a recording film capable of being changed to an opticallydifferent state by irradiation with an energy beam to thereby recordinformation, the method being provided for recording information as arecording mark length and (preceding and following) space lengths (markdistance) in the optically different state by irradiating the recordingfilm with a multi-pulse chain of the energy beam having at least twoemission power levels each having an emission time changed in accordancewith the optical disk while relatively moving the energy beam in asurface of the recording film of the optical disk, wherein informationis recorded while the position and width of the first pulse in themulti-pulse chain of the energy beam are changed suitably independentlyin accordance with the recording mark length and the preceding spacelength. In addition to this configuration, in the optical disk recordingmethod, information may be recorded while the position and/or width ofthe last pulse in the multi-pulse chain are changed suitably inaccordance with the recording mark length and the following spacelength.

In the optical disk recording method, a mono pulse is used for recordingthe shortest mark so that information is recorded while the position andwidth of the mono pulse are changed suitably in accordance with thepreceding space length and the following space length. Or in the opticaldisk recording method, information is recorded while the pulse riseposition of the mono pulse is changed suitably in accordance with thepreceding space length and the pulse fall position of the mono pulse ischanged suitably in accordance with the following space length.

There is also provided an optical disk device having an energy beamgenerator, a power adjusting unit by which emission power of an energybeam generated by the energy beam generator can be set to have at leasttwo predetermined power levels, a holding mechanism for holding anoptical disk having a recording film capable of being changed to anoptically different state by irradiation with the energy beam having thepredetermined power levels to thereby record information, a moving unitby which the energy beam can be relatively moved in a surface of therecording film of the optical disk, and a conversion unit for convertinginformation to be recorded into a power level change of the energy beam,wherein: the optical disk device further has a storage unit for storingvalues of settings concerning energy beam emission control; the storageunit includes at least two reference tables on which the position andwidth of the first pulse in the multi-pulse chain are defined on thebasis of the recording mark length and the preceding space length; andthe power adjusting mechanism performs emission pulse timing controlwhile referring to the tables. In addition to this configuration, thestorage unit further includes at least one reference table on which theposition and/or width of the last pulse in the multi-pulse chain aredefined on the basis of the recording mark length and the followingspace length; and the power adjusting mechanism performs emission pulsetiming control while referring to the tables.

In the optical disk device, the storage unit may further include atleast two reference tables on which the position and width of the monopulse are defined on the basis of the preceding space length and thefollowing space length; and the power adjusting mechanism performsemission pulse timing control while referring to the tables.

Or in the optical disk device, the power adjusting mechanism may performemission pulse timing control on the basis of the pulse rise timing ofthe mono pulse decided by referring to the reference table concerningthe position or width of the first pulse and the pulse fall timing ofthe mono pulse decided by referring to the reference table concerningthe position or width of the last pulse.

The optical disk may be configured so that each of the reference tablesholds values of coefficients expressed as integers in a definitionalequation for defining the position or width of each pulse. Particularly,the position and/or width of each pulse are expressed as the sum of alinear term and a nonlinear term with respect to twofold increase inrecording velocity. The coefficient of the linear term is held or thedifference of the coefficient of the linear term from a predeterminedvalue is held.

There is further provided an optical disk which is configured so thatthe reference tables are partially or wholly recorded in a predeterminedposition of the disk in advance.

There is further provided an information recording method for recordinginformation by irradiating an information recording medium with anenergy beam, wherein: a recording mark is formed by irradiating theinformation recording medium with at least first and last pulses in amulti-pulse chain obtained by changing power of the energy beampulsatively; and information is recorded on the information recordingmedium on the basis of one case selected from cases 1 to 8:

case 1 where TLFP is changed while TEFP is fixed and where TLLP ischanged while TSLP is fixed;

case 2 where TEFP is changed while TLFP is fixed and where TLLP ischanged while TSLP is fixed;

case 3 where TLFP is changed while TEFP is fixed and where TSLP ischanged while TLLP is fixed;

case 4 where TEFP is changed while TLFP is fixed and where TSLP ischanged while TLLP is fixed;

case 5 where TLFP is changed while TEFP is fixed;

case 6 where TEFP is changed while TLFP is fixed;

case 7 where TLLP is changed while TSLP is fixed; and

case 8 where TSLP is changed while TLLP is fixed;

when TLFP is the irradiation time of the first pulse, TEFP is the amountof displacement of the pulse fall timing of the first pulse from areference time point, TLLP is the irradiation time of the last pulse,and TSLP is the amount of displacement of the pulse rise timing of thelast pulse from a reference time point.

Incidentally, in the optical disk recording method and the optical diskdevice according to the invention, a modulation code mark small in theminimum mark/space length relative to the detection window width can berecorded accurately on various recording media different in recordingfilm material or recording mechanism or on high-speed recordable mediawhich will appear in the future, when numerical values of parameters arechanged without any change in configuration of the fundamental waveform.Particularly, it is possible to compensate for mark edge shift caused bythermal interference at the time of recording and mark edge shift causedby resolving power at the time of reproducing. In the optical diskaccording to the invention, it is possible to operate the optical diskrecording method and the optical disk device easily.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view showing a recording strategy correspondingto modulation of RLL(1, 7), in an optical disk recording methodaccording to a first embodiment of the invention;

FIG. 2 is an explanatory view showing a recording strategy correspondingto modulation of RLL(2, 10), in a conventional optical disk recordingmethod;

FIG. 3 is an explanatory view showing a recording pulse of 2Tw in theoptical disk recording method according to a third embodiment of theinvention;

FIG. 4 is a block diagram showing a specific example of an optical diskdevice according to the invention;

FIG. 5 is a table for comparing the two modulation methods RLL(1, 7) andRLL(2, 10) in the case where transfer time T is set to be 24 ns per userbit;

FIG. 6 is a table for illustrating a reference table of parametersconcerning the first pulse in the first embodiment depicted in FIG. 1;

FIG. 7 is a table for illustrating a reference table of parametersconcerning the last pulse in the first embodiment depicted in FIG. 1;

FIG. 8 is a table for illustrating a reference table of parametersconcerning a recording pulse of 2Tw in a second embodiment of theinvention;

FIG. 9 is a table for illustrating a reference table of parametersconcerning the last pulse in the third embodiment of the invention;

FIG. 10 is a view for explaining a recording strategy in a fourthembodiment of the invention; and

FIG. 11 is a view for explaining another recording strategy in thefourth embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

First and second embodiments of the invention will be described belowwith reference to the drawings.

FIG. 4 shows an optical disk device according to the invention. In FIG.4, the reference numeral 100 designates an optical disk; 110, a spindlemotor; 112, a chucking mechanism; 115, a guide rail; 116, a feed motor;117, an optical pickup; 121, an objective lens actuator; 131, asemiconductor laser; 132, a collimator lens; 133, a beam splitter; 134,a detection lens; 135, a photo detector; 136, an objective lens; 150, asystem controller; 151, a servo controller; 152, an amplifier; 153, adecoder; 154, a signal processing circuit; 155, a delay circuit; 156,current sinks; 157, a constant current source; 158, an output terminal;159, an input terminal; 160, a power supply terminal; 161, a signalprocessing circuit; and 170, a binarization circuit.

An optical disk recording method according to a first embodiment of theinvention will be described.

FIG. 1 shows a recording strategy in the optical disk recording methodaccording to the invention. In this embodiment, there is shown the casewhere information is recorded after converted into RLL(1, 7) as amodulation code. When Tw is the time width (detection window width) of areference clock pulse for recording and reproducing data, the smallestmark or space length is 2Tw (twice as large as the time Tw) and thelargest mark or space length is generally 8Tw.

When an NRZI signal expressing time-series information to be recorded inthe optical disk is given, the NRZI signal is converted into atime-series energy beam power level change, that is, an emission pulsewaveform by a suitable signal processing circuit.

Three power levels, namely, a recording power level Pw, a first biaspower level Pb1 and a second bias power level Pb2, are set on theassumption that a rewritable phase change material having good overwritecharacteristic is used as the material of a recording film. The state ofthe recording film can be shifted reversibly so that the recording filmgets into a first state (mark in this embodiment) when the recordingfilm is irradiated with an energy beam of the recording power level Pw,and that the recording film gets into a second state (space in thisembodiment) when the recording film is irradiated with an energy beam ofthe second bias power level Pb2. The first bias power level Pb1 is equalto or lower than the second bias power level Pb2.

When the length of a mark (region of the first state) to be formed inthe recording film is not smaller than 3Tw (i.e. the length of the NRZIsignal is not smaller than 3Tw), a period of the first bias power levelPb1 is mixed with an irradiation period of the recording power level Pwso that the energy beam can be provided in the form of a multi-pulsechain. In the multi-pulse chain of the energy beam, a light pulsegenerated first is called first pulse, and a light pulse generated lastis called last pulse. Repeated light pulses which come and go betweenthe recording power level Pw and the first bias power level Pb1 areprovided between the first pulse and the last pulse in accordance withthe length of the NRZI signal. The number of repetitions is (n−3) whennTw (n>4) is the length of the NRZI signal. The repeated pulses providedbetween the first and last pulses are generically referred to as combpulse chain.

Collectively, the total number of light pulses to be generated forforming a mark corresponding to the NRZI signal having a length of nTwis (n−1). Particularly, when a mark corresponding to the NRZI signalhaving a length not smaller than 4Tw needs to be formed, a first pulse,a comb pulse chain and a last pulse are generated as recording pulses.When a mark corresponding to the NRZI signal having a length of 3Twneeds to be formed, a first pulse and a last pulse are generated asrecording pulses. When a mark corresponding to the NRZI signal having alength of 2Tw needs to be formed, a mono pulse is generated as arecording pulse.

When the length of the NRZI signal is not smaller than 3Tw, the energybeam is kept at the first bias power level Pb1 for a predetermined timeafter the last pulse is generated. When the length of the NRZI signal is2Tw, the energy beam is kept at the first bias power level Pb1 for apredetermined time after the recording pulse is generated.

Incidentally, when an optical disk having a recording film made ofanother material such as an organic coloring material than the phasechange material is used, the state of the recording film cannot beshifted from the first state to the second state even in the case wherethe recording film is irradiated with an energy beam of the second biaspower level Pb2. In this case, there may be used a recording strategy inwhich only two power levels, namely, a recording power level Pw and afirst bias power level Pb1 are set.

Use of a non-recordable bias power level, however, may permitimprovement in recording characteristic. For example, if the output ofthe energy beam is particularly limited at the time of high-speedrecording, it may be impossible to sufficiently increase the temperatureof the recording film by pulse irradiation of the recording power levelPw. Recording is however enabled easily when the bias power level isused for preheating the recording film before recording in order toassist the temperature rise at the time of recording. Accordingly, therecording strategy having the three power levels as shown in FIG. 1 canbe also used for a recordable optical disk having the state changingirreversibly.

Next, definitions of time points (positions) and irradiation timeperiods (widths) of the first and last pulses in this embodiment will bedescribed. The pulse rise time point of the first pulse is defined as atime point which is a displacement time period dTtop ahead of areference time point which is 1Tw after the rise time point of the NRZIsignal. Incidentally, in the case where the first pulse rises when adisplacement time period dTtop has passed after the reference timepoint, the pulse rise time point of the first pulse is regarded ashaving a negative value. The irradiation time period Ttop of the firstpulse is defined as a time period between the pulse rise time point ofthe first pulse and the pulse fall time point of the first pulse. On theother hand, the pulse rise time point of the last pulse is defined as atime point which is a displacement time period dTlp ahead of a referencetime point which is 1Tw ahead of the fall time point of the NRZI signal.Incidentally, in the case where the last pulse rises when a displacementtime period dTlp has passed after the reference time point, the pulserise time point of the last pulse is regarded as having a negativevalue. The irradiation time period Tlp of the last pulse is defined as atime period between the pulse rise time of the last pulse and the pulsefall time point of the last pulse.

In this embodiment, the recording pulse of 2Tw is defined in accordancewith the definition of the first pulse.

The comb pulse chain is formed so that each pulse rises at a time pointcorresponding to a reference clock position and falls at a time pointwhich is a time period Tmp after the pulse rise time point.

The irradiation time point of the first bias power level after the lastpulse is defined as a time point which is a displacement time period dTeahead of the fall time point of the NRZI signal as a reference timepoint. Incidentally, the first bias power level rises when adisplacement time period dTe has passed after the reference time point,the irradiation time point is regarded as having a negative value.

In this embodiment, each of the values of dTtop, Ttop, dTlp, Tlp, Tmpand dTe is defined by the sum of a linear term and a nonlinear term withrespect to the reference clock Tw. For example, dTtop is defined asfollows:dTtop=a·Tw/n+b·tin which n is a predetermined integer, Tw/n is pulse resolving power, tis a predetermined time independent of Tw, and a and b are coefficientsfor the respective terms. In this embodiment, the coefficients a and bare integers.

Incidentally, the invention is not limited thereto. For example, eachparameter may be defined only by the linear term with respect to thereference clock Tw or may be defined only by the nonlinear term,conversely. The parameters may include parameters each defined by thesum of the linear term and the nonlinear term may be mixed, andparameters each defined only by the linear term.

Incidentally, each of dTtop, Ttop, dTlp, Tlp, Tmp and dTe for definingthe recording pulse timing does not always take a constant value.

To compensate for mark edge shift caused by thermal interference betweenadjacent marks at the time of recording data and shortage of resolvingpower at the time of reproducing data, for example, in the DVD-RAM orthe like, parameters for defining the pulse rise time point of the firstpulse and the pulse fall time point of the last pulse were often changedadaptively in accordance with the combination of NRZI signals though thedefinitions of pulse timing were not always the same as in thisembodiment. Particularly, the first pulse was often translated in thedirection of the time axis without any change of the irradiation timeperiod or the pulse rise time point of the first pulse was often changedwhile the pulse fall time point was fixed. Similarly, the last pulse wasoften translated without any change of the irradiation time point or thepulse fall time point of the last pulse was often changed while thepulse rise time point was fixed.

As described above, particularly in a next-generation optical disk whichis assumed in the invention and in which the smallest mark/space lengthwill be 0.1 μm or smaller, it is however difficult to record data alwaysstably because thermal interference between adjacent marks becomes moreintensive at the time of recording data. Particularly in the recordablerecording film, front edge shift of the mark caused by the difference inpreceding space length is remarkable because the recordable recordingfilm has characteristic that the recording film is easily affected bythermal interference.

Also in the next-generation optical disk which is assumed in theinvention and in which the smallest mark/space length will be 2Tw,deterioration of reproducing performance caused by mark edge shift of aplayback signal becomes remarkable because resolving power of playbacklight spots is reduced at the time of reproducing data. It was oftenimpossible to perform sufficient correction by the conventional method.

Therefore, in this embodiment, a reference table of dTtop and areference table of Ttop are defined independently as shown in FIG. 6particularly to correct remarkable front edge shift. As a result, therecording mark length and the preceding space length can be combinedwith each other so that the position and width of the first pulse can bedefined freely. Accurate edge shift correction can be made on thenext-generation optical disk larger in interference, so thatrecording/reproducing performance can be improved.

Particularly in this embodiment, a reference table concerning thecoefficient (coefficient a in the aforementioned example of dTtop) ofthe linear term with respect to Tw in each parameter is defined. Sincethe coefficient is an integer, there is a merit that the quantity ofinformation to be recorded can be suppressed, and that it is easy tocope with the situation that Tw changes according to a plurality ofrecording speeds at the time of recording data at a constant angularvelocity (CAV).

Or a reference value of each parameter may be defined in advance so thatthe amount of displacement from the reference value can be registered ineach reference table. For example, a reference table of dTtop may bedefined as follows. First, dTtop is defined again by the followingexpression:dTtop=(a0+Δa)Tw/n+b·tin which a0 is a reference value (integer), and Δa is a displacementamount (integer). Then, the reference table is defined with respect toΔa.

As for the rear edge shift, a reference table of dTlp or a referencetable of Tlp is defined as shown in FIG. 7. Or configuration may be madeso that one of the reference table of dTlp and the reference table ofTlp can be switched, for example, in accordance with the difference inthe recording film material of the optical disk. Particularly in therecordable recording film made of an organic coloring material,correction control of the rear edge need not be performed accuratelybecause the recording film has characteristic that the recording film islittle affected by the difference in following space length. When thesame rear edge correction as in the conventional technique is howeverperformed, sufficient rear edge shift correction can be made on thephase change recording medium assumed in this embodiment.

Incidentally, the reference table concerning dTlp and the referencetable concerning Tlp may be defined independently in the same manner asin the first pulse. In this case, the number of variables in recordingstrategy increases but the position and width of the last pulse waveformcan be defined freely.

In this embodiment, as a reference table concerning the first pulse,there is provided a 4×3 reference table on which the preceding spacelength is classified into four groups, namely, 2Tw, 3Tw, 4Tw and 5Tw orlarger and on which the recording mark length is classified into threegroups, namely, 2Tw, 3Tw and 4Tw or larger, as shown in FIG. 6. As areference table concerning the last pulse, there is provided a 4×2reference table on which the following space length is classified intofour groups, namely, 2Tw, 3Tw, 4Tw and 5Tw or larger and on which therecording mark length is classified into two groups, namely, 3Tw and 4Twor larger, as shown in FIG. 7. It is however a matter of course that theinvention is not limited thereto, and that the size of each referencetable may be defined desirably in consideration of the degree ofdependence on the space length and recording mark length and thecorrection effect.

Although this embodiment has been described on the case where timing ofeach pulse is defined by the pulse rise time point and irradiation timeperiod of the pulse, the invention does not depend on the way ofdefining timing of each pulse. For example, timing of each pulse may bedefined by the pulse rise time point and the pulse fall time point, bythe pulse fall time point and irradiation time period of the pulse, orby the irradiation time period and central time point of the irradiationtime.

According to the invention, accurate mark edge compensation can be madewhen reference tables shown in this embodiment are provided.Accordingly, various optical disks different in recording film materialor recording mechanism can be used when only pulse timing parametersincluding the power levels and the reference tables are changed withoutany change of the fundamental waveform.

The optical disk recording method as a second embodiment of theinvention will be described below.

In this embodiment, the time point (position) and irradiation timeperiod (width) of a recording pulse of 2Tw are defined independent ofthe pulse chain of 3Tw or larger. That is, let dTop2 be the pulse riseposition of the recording pulse and let Ttop2 be the irradiation timeperiod of the recording pulse. With respect to dTtop2 and Ttop2, areference table as shown in FIG. 8 is defined independently inaccordance with the combination of the preceding space length and thefollowing space length. Incidentally, a reference table of dTop and Ttopis defined on the basis of the recording mark length of 3Tw or larger.

When the recording pulse of 2Tw is defined by the combination of thepreceding space length and the following space length as describedabove, dependence of rear edge shift of a 2Tw mark on the followingspace length can be compensated though the dependence cannot becompensated in the first embodiment. The other configuration of thesecond embodiment is the same as that of the first embodiment.Accordingly, description of the other configuration and function will beomitted.

The optical disk recording method as a third embodiment of the inventionwill be described below.

In this embodiment, parameters are defined in the condition that therecording pulse of 2Tw is regarded as a superposition of the first pulseand the last pulse as shown in FIG. 3. That is, the pulse rise timepoint of the recording pulse of 2Tw is defined on the basis of the timepoint (position) dTtop of the first pulse, and the pulse fall time pointis defined on the basis of the irradiation time period (width) Tlp ofthe last pulse.

The irradiation time period (width) Ttop of the first pulse and the timepoint (position) dTlp of the last pulse are set as specific values inaccordance with the recording disk. Incidentally, the parameters aredefined so that the first pulse does not exceed the rear edge and thelast pulse does not exceed the front edge, and that the first pulse andthe last pulse are not separated as two pulses.

Or the parameters are defined so that the irradiation time period of thefirst pulse is always set to be equal to the irradiation time period ofthe last pulse, and that the pulse rise time point of the last pulse isalways set to be equal to the pulse rise time point of the first pulse.That is, while the first pulse and the last pulse are made coincidentwith each other, the pulse rise time point of the combined pulse ischanged in accordance with the preceding space length and the pulse falltime point of the combined pulse is changed in accordance with thefollowing space length.

With respect to a reference table of dTlp and Tlp for defining the lastpulse, as shown in FIG. 9, the recording mark length is classified intothree groups inclusive of the recording mark length of 2Tw. The otherconfiguration of the third embodiment is the same as that of the firstembodiment. Accordingly, description of the other configuration andfunction will be omitted.

When the recording pulse of 2Tw is defined as a superposition of thefirst pulse and the last pulse as described above, the dependence ofrear edge shift of the 2Tw mark on the following space length can becompensated without increase in the number of reference tables asrequired in the second embodiment. Incidentally, there is an effect thatthe recording pulse of 2Tw can be handled so as to be unified with themulti-pulse chain of 3Tw or larger.

An optical disk device and an optical disk as a fourth embodiment of theinvention will be described below with reference to the drawings.

FIG. 4 is a block diagram of an optical disk device according to theinvention. A removable optical disk 100 is held by a chucking mechanism112 provided in a spindle motor 110. When the spindle motor 110 isdriven, the optical disk 100 rotates so that the position of the opticaldisk 100 is moved relative to an energy beam emitted from an opticalpickup 117. When a feed motor 116 is driven, the optical pickup 117 canmove linearly along a guide rail 115 substantially in a radial directionof the optical disk 100.

The optical pickup 117 is provided with a semiconductor laser 131 whichserves as an energy beam generator. An energy beam emitted from thesemiconductor laser 131 is transmitted through a collimator lens 132 anda beam splitter 133 and converged by an objective lens 136. Theobjective lens 136 is held by an objective lens actuator 121 so that theobjective lens 136 can be displaced or positioned both in a direction(focusing direction) perpendicular to a recording surface of the opticaldisk 100 and in a radial direction (tracking direction) of the disk.Accordingly, the energy beam can be converged into a predeterminedposition of the optical disk 100.

Part of the energy beam converged on the recording surface of theoptical disk 100 is reflected and transmitted through the objective lens136 again. Then, the part of the energy beam is reflected on the beamsplitter 133 and converged by a detection lens 134, so that the lightintensity of the energy beam is detected by a photo detector 135. Alight-receiving region of the photo detector 135 is separated into aplurality of light-receiving regions. The light intensity detected byeach light-receiving region is amplified by an amplifier 152 andsubjected to an arithmetic operation. As a result, information (a servosignal) concerning the position of the optical disk 100 relative to alight spot converged by the objective lens 136 and an informationplayback signal are detected. The servo signal is sent to a servocontroller 151. The playback signal is sent to a decoder 153.

When the optical disk 100 mounted in the optical disk device is fixed bythe chucking mechanism 112, a detector 140 operates so that a signaldetected by the detector 140 is sent to a system controller 150. Uponreception of the signal, the system controller 150 controls the spindlemotor 110 to rotate the optical disk 100 at a predetermined rotationalvelocity. The system controller 150 further controls the feed motor 116to locate the optical pickup 117 in a predetermined position. The systemcontroller 150 further controls the semiconductor laser 131 to emitlight and controls the feed motor 116 through the servo controller 151to drive the objective lens actuator 121 so that the focal spot formedby the objective lens 136 is aligned with the predetermined position ofthe optical disk 100. Then, the servo controller 151 generates a signalindicating the fact that the focal spot is formed on the recordingsurface of the optical disk 100, and sends the signal to the systemcontroller 150. The system controller 150 operates the decoder 153 todecode the playback signal. When a reproduced track is not aninformation track in a control zone, the system controller 150 operatesthe servo controller 151 so that the focal spot is positioned on aninformation track in a control zone. As a result of the aforementionedoperation, the system controller 150 reproduces the information track ina control zone of the optical disk 100 and reads disk informationconcerning recording.

The optical disk 100 is an optical disk according to the invention. Diskinformation concerning recording is recorded on the information track inthe control zone in advance. That is, parameters in recording strategyshown in FIG. 1 and reference tables as described above in the first tothird embodiments are recorded as the disk information. If necessary,flags indicating reference table types (as to whether values on eachtable are coefficients or differences) may be further recorded as thedisk information. In this embodiment, the optical disk can be operatedeasily on the basis of the disk information.

The system controller 150 reads the information concerning recording,that is, information concerning recording power levels, time relationsof recording pulses, reference tables and flags and writes theinformation in a parameter table of a signal processing circuit 154, aparameter table of a delay circuit 155 and current sink amountparameters of current sinks 156. Particularly, the delay circuit 155 orthe combination of the delay circuit 155 and the signal processingcircuit 154 serves as a storage unit for storing reference tables in theinvention.

Incidentally, the processes in which the system controller 150 readsparameters of recording strategy of the optical disk 100 and writes theparameters in the parameter table of the signal processing circuit 154,the parameter table of the delay circuit 155 and the current sink amountparameters of the current sinks 156 may be performed only in the casewhere the optical disk 100 is write-enabled. That is, these processesmay be dispended with in the case where the optical disk 100 iswrite-disabled.

When an information playback command is given from an upper controllerthrough an input connector 159, the system controller 150 instructs theservo controller 151 to locate the focal spot on an appropriate positionof the optical disk 100. After the playback signal obtained by the photodetector 135 is decoded, the playback information is sent to the uppercontroller through an output connector 158.

When an information recording command is given from the upper controllerthrough the input connector 159, the system controller 150 instructs theservo controller 151 to locate the focal spot on an appropriate positionof the optical disk 100. Information to be recorded is converted into anNRZI signal by a signal processing circuit 161. The NRZI signal isfurther converted into suitable pulse trains by the signal processingcircuit 154. When these pulse trains pass through the delay circuit 155,predetermined delays are given to these pulse trains respectively. Thedelayed pulse trains are transmitted to the current sinks 156.

A constant current source 157 is connected to the semiconductor laser131. The current sinks 156 are connected to the constant current source157. Configuration is made so that the total current spent by thesemiconductor laser 131 and the current sinks 156 is always constant.Whether the current sinks 156 are operated to absorb the current or not,depends on the signal generated by the signal processing circuit 154 andtransmitted through the delay circuit 155. When the current sinks 156operate, part of the current provided from the constant current source157 is absorbed to the current sinks 156. As a result, the amount of thecurrent supplied to the semiconductor laser 131 is reduced to therebychange the power level of the energy beam emitted from the semiconductorlaser 131. When the current sinks 156 are operated at suitable timing,the signal processing circuit 154 and the delay circuit 155 achieve therecording strategy of the invention shown in FIG. 1. That is, theoptical disk recording method described in any one of the first to thirdembodiments can be achieved by the optical disk device according to thisembodiment, so that accurate edge shift correction of next-generationoptical disks larger in interference can be made particularly in termsof downward compatibility in which low-speed recording is made on futurehigh-speed recording disks, and that various optical disks different inrecording film material or recording mechanism can be used without anychange of the fundamental waveform of the recording strategy.

Incidentally, to perform the aforementioned operation, the optical diskdevice according to this embodiment is supplied with external electricpower through a terminal 160.

The optical disk recording method as the fourth embodiment of theinvention will be described below.

Referring to FIG. 10, change with time in power level of the energy beamapplied on the recording medium will be described in the case whereinformation converted into RLL(1, 7) as a modulation code is recorded onthe recording medium. The way of changing the power level with thepassage of time at the time of recording information is generallyreferred to as “write strategy” or “recording strategy”. FIG. 10 shows arecording strategy including the information recording method accordingto the invention. Specifically, the recording strategy will be describedon the case where a phase change medium which is a rewritable medium istaken as an example. In this case, the shortest mark/space length is 2Tw(twice as large as the time Tw) and the longest mark/space length isgenerally 8 Tw when Tw is the time width of a reference clock atrecording/reproducing.

When an NRZI signal is given as time-series information to be recordedon the recording medium, the NRZI signal is converted into a time-seriespower level change of the energy beam by a suitable signal processingcircuit. The time-series power level change is shown as a light pulsewaveform in FIG. 10. Four levels “Write Level”, “Bias Level 1”, “BiasLevel 2” and “Bias Level 3” are set as the power levels. In the “BiasLevel 1”, the recording medium can be shifted to a first state. In the“Write Level”, the recording medium can be shifted to a second state.The “Bias Level 3” is equal to or lower than the “Bias Level 1”. Whenthe length of a region of the second state formed in the recordingmedium is 3Tw or larger (i.e. the length of the NRZI signal is 3Tw orlarger), a period of the power level “Bias Level 3” is mixed with theirradiation period of the “Write Level” so that the energy beam isprovided as a multi-pulse chain. The first light pulse in themulti-pulse chain of the energy beam is referred to as “first pulse”.The last light pulse in the multi-pulse chain is referred to as “lastpulse”. Repeated light pulses reciprocating between the “Write Level”and the “Bias Level 3” are provided between the first pulse and the lastpulse in accordance with the length of the NRZI signal. The number ofrepetitions is (n−3) when the length of the NRZI signal is nTw (n>2).The repeated pulses provided between the first pulse and the last pulseare generically referred to as “comb pulse chain”. That is, when aregion of the second state corresponding to the NRZI signal having alength of 4Tw or larger is formed, a recording pulse chain is providedas a combination of the first pulse, the comb pulse chain and the lastpulse. When a region of the second state corresponding to the NRZIsignal having a length of 3Tw is formed, a recording pulse chain isprovided as a combination of the first pulse and the last pulse. When aregion of the second state corresponding to the NRZI signal having alength of 2Tw is formed, a recording pulse chain is provided as a monopulse.

The “Bias Level 2” is a power level which is equal to or lower than the“Bias Level 1” and which is equal to or higher than the “Bias Level 3”.When the length of a region of the second state is 3Tw or larger, thepower level of the energy beam is kept at the “Bias Level 2” for apredetermined time after the last pulse. When the length of a region ofthe second state is 2Tw, the power level of the energy beam is kept atthe “Bias Level 2” for a predetermined time after the write light pulse.

There is a possibility that the “Bias Level 2” may be a power levelequal to either “Bias Level 1” or “Bias Level 3”. There is a possibilitythat all the “Bias Level 1”, “Bias Level 2” and “Bias Level 3” may bequite the same power level. Reference values of the “Write Level”, “BiasLevel 1”, “Bias Level 2” and “Bias Level 3” may be recorded as mediuminformation in suitable positions of the recording medium in advance.The portion in which medium information concerning recording strategy isrecorded on the recording medium is referred to as an information trackin a control data zone. Reference values of the power levels are readfrom the information track in the control data zone of the recordingmedium, so that the power levels at the time of writing data are decidedon the basis of the reference values.

In FIG. 10, definition of a recording waveform is conceived inconsideration of the case where a region of the second statecorresponding to the NRZI signal having a length of 3Tw or larger isformed. The pulse fall timing of the first pulse in a write pulse trainis defined as a time point that TEFP has passed after the rise timing ofthe NRZI signal. The pulse rise timing of the first pulse is at a timepoint which is a time period TLFP ahead of the pulse fall time point ofthe first pulse. The pulse rise timing of the last pulse in the writepulse train is at a time point that a time period TSLP has passed aftera reference time point which is 1Tw ahead of the fall time point of theNRZI signal. The pulse fall timing of the last pulse is at a time pointthat a time period TLLP has passed after the pulse rise time point ofthe last pulse.

A comb pulse chain may be provided between the first pulse and the lastpulse. The pulse rise timing of each of pulses in the comb pulse chaincoincides with a reference clock position. The pulse fall timing of eachpulse is at a time point that a time period TTMP has passed after thepulse rise time point of the pulse.

The case where a region of the second state corresponding to the NRZIsignal having a length of 2Tw is formed in the recording medium will beconsidered. The pulse rise timing of the light pulse is at a time pointwhich is a time period TLFP ahead of a reference time point that TELPhas passed after the rise timing of the NRZI signal. The pulse falltiming of the last pulse in the write pulse train, that is, the pulsefall timing of the light pulse is at a time point that a time periodTLLP has passed after a second reference time point which is a timepoint that a time period TSLP has passed after a reference time pointwhich is 2Tw ahead of the fall time point of the NRZI signal.

A portion having a power level of “Bias Level 2” follows the last pulsein the pulse train of 3Tw or larger or the recording pulse in the pulsetrain of 2Tw. The length of the portion is TLE.

TEFP, TLFP, TSLP, TLLP, TLE and TTMP which are time periods for definingthe recording pulse train are decided on the basis of informationconcerning the recording method, the information recording medium andthe standard information recording apparatus, which is read from theinformation track in the control data zone of the recording medium.

Description has been made on the case where a phase change medium istaken as an example. That is, the first recording state or the secondrecording state corresponds to either crystalline state ornon-crystalline state. There is exhibited overwrite characteristic inwhich the mark is erased by the “Bias Power 2”. In a recordable medium,the temperature of the recording film is increased by the “Peak Power”to change the optical characteristic of the recording film. Accordingly,even in the case where the recording film is irradiated with an energybeam of “Bias Power” after the optical characteristic of the recordingfilm has been once changed, the mark cannot be erased. Even in therecordable medium, it is however possible to improve recordingcharacteristic when a non-recordable “Bias Power” level is used. Thatis, when recording is to be made at a high speed, there is a possibilitythat the temperature of the recording film cannot be increased byirradiation with an energy beam of the “Peak Power” level. Particularly,when the output of the laser power is limited, the “Peak Power” islimited. In this case, when preheat is given by the “Bias Power” beforerecording in order to assist the temperature rise at the time ofrecording, recording can be made easily. Accordingly, even in therecordable medium, the waveform with the “Bias Power” shown in FIG. 10can be used as recording strategy.

TEFP, TLFP, TSLP, TLLP, TLE and TTMP which are time periods for definingthe recording pulse train are not always constant. It is necessary tochange these time periods in accordance with a combination of NRZIsignals. In the case of high-density recording, it is difficult toperform always stable recording because thermal interference betweenadjacent marks becomes large. It is therefore conceived that therecording waveform is changed adaptively in accordance with thecombination of NRZI signals. This measure is particularly effective onthe recordable medium having characteristic in which the medium iseasily affected by thermal interference.

To correct the front edge shift, either TEFP or TLFP is changed. Theamounts of change from the reference values of TEFP and TLFP arereferred to as ΔTEFP and ΔTLFP respectively. To correct the rear edgeshift, either TSLP or TLLP is changed. The amounts of change from thereference values of TSLP and TLLP are referred to as ΔTSLP and ΔTLLPrespectively.

A first look-up table of TMF concerning the front edge is defined. Onthe first look-up table, values decided by combinations of M(n) andS(n−1) are arranged when M(n) is the length of a mark to be currentlyrecorded, and S(n−1) is the length of a preamble space preceding themark. The values may be positive or negative. Then, a second look-uptable of TML concerning the rear edge shift is defined. On the secondlook-up table, values decided by combinations of M(n) and S(n+1) arearranged when M(n) is the length of the mark to be currently recorded,and S(n+1) is the length of a following space following the mark. Thevalues may be positive or negative.

In case 1, the value of TMF is made coincident with the value of ΔTLFP,and the value of TML is made coincident with the value of ΔTLLP. In thiscase, the value of TLFP and the value of TLLP are changed in accordancewith the combination of NRZI signals. That is, the pulse rise positionof the first pulse is changed while the pulse fall position of the firstpulse is fixed. Further, the pulse fall position of the last pulse ischanged while the pulse rise position of the last pulse is fixed.

In case 2, the value of TMF is made coincident with the value of ΔTEFP,and the value of TML is made coincident with the value of ΔTLLP. In thiscase, the value of TEFP and the value of TLLP are changed in accordancewith the combination of NRZI signals. That is, both pulse rise positionand pulse fall position of the first pulse are changed simultaneously.Further, the pulse fall position of the last pulse is changed while thepulse rise position of the last pulse is fixed.

In case 3, the value of TMF is made coincident with the value of ΔTLFP,and the value of TML is made coincident with the value of ΔTSLP. In thiscase, the value of TLFP and the value of TSLP are changed in accordancewith the combination of NRZI signals. That is, the pulse rise positionof the first pulse is changed while the pulse fall position of the firstpulse is fixed. Further, both pulse rise position and pulse fallposition of the last pulse are changed simultaneously.

In case 4, the value of TMF is made coincident with the value of ΔTEFP,and the value of TML is made coincident with the value of ΔTSLP. In thiscase, the value of TEFP and the value of TSLP are changed in accordancewith the combination of NRZI signals. That is, both pulse rise positionand pulse fall position of the first pulse are changed simultaneously.Further, both pulse rise position and pulse fall position of the lastpulse are changed simultaneously.

In case 5, the value of TMF is made coincident with the value of ΔTLFP.In this case, the value of TLFP is changed in accordance with thecombination of NRZI signals. That is, the pulse rise position of thefirst pulse is changed while the pulse fall position of the first pulseis fixed.

In case 6, the value of TMF is made coincident with the value of ΔTEFP.In this case, the value of TEFP is changed in accordance with thecombination of NRZI signals. That is, both pulse rise position and pulsefall position of the first pulse are changed simultaneously.

In case 7, the value of TML is made coincident with the value of ΔTLLP.In this case, the value of TLLP is changed in accordance with thecombination of NRZI signals. That is, the pulse fall position of thelast pulse is changed while the pulse rise position of the last pulse isfixed.

In case 8, the value of TML is made coincident with the value of ΔTSLP.In this case, the value of TSLP is changed in accordance with thecombination of NRZI signals. That is, both pulse rise position and pulsefall position of the last pulse are changed simultaneously.

Information for selection of values from the values contained in thefirst and second look-up tables and selection of one case from the cases1 to 8 is decided when information written in the information track inthe control data zone of the recording medium is read.

As described above, when adaptive waveform change using the look-uptables is classified into cases 1 to 8 so that one case can be selectedfrom the cases 1 to 8, there is an effect that a method adapted tovarious recording media different in characteristic can be provided sothat information can be recorded always stably with good compatibility.

In this embodiment, in the definition of the first look-up table, M(n)is classified into four cases and S(n−1) is classified into four cases,that is, the first look-up table has a 4×4 size in total. In thedefinition of the second look-up table, M(n) is classified into fourcases and S(n+1) is classified into four cases, that is, the secondlook-up table has a 4×4 size in total. The size of each look-up table isnot limited to 4×4. The effect of the invention can be obtained as longas the size of the look-up table is not 1×1.

This write strategy has characteristic that recording can be made at acurrent linear velocity based on this write strategy even in the casewhere a recordable high-speed medium will be developed in the future.That is, the recordable high-speed medium cannot but have a heat storagestructure to restrain the recording power from being increased by thehigh speed. Accordingly, when recording is to be made at a low speed,heat is stored in the recordable high-speed recording medium so that theamount of thermal interference becomes large. Therefore, when thestrategy of the invention for suppressing thermal interference is used,the high-speed medium which will be developed in the future can be usedin low-speed recording so that downward compatibility can be kept good.

If the write strategy currently discussed can be used for the high-speedmedium which will be developed in the future when only numerical valuesof parameters are changed without any change of the fundamental shape ofthe write strategy, it is unnecessary to provide a plurality of circuitseach for reading strategy and parameters written in the controlinformation area of each disk in accordance with generation andgenerating a waveform from the NRZI to the laser drive circuit.Particularly, in a constant angular velocity (CAV) method in whichinformation is recorded/reproduced at a constant rotational velocity,the linear velocity varies according to the radial position. It istherefore necessary to use one and the same fundamental strategy on thewhole surface of the disk in order to set parameters smoothly inaccordance with the radius. When the velocity becomes high, the rise andfall characteristic of the laser drive circuit is limited. For thisreason, in the strategy shown in FIG. 10, the waveform of T_(MP) in themulti-pulse chain changes from a rectangular wave shape to a triangularwave shape, so that irradiation energy becomes insufficient in thisportion. As a method to compensate for the shortage of irradiationenergy, as shown in FIG. 11, there is provided a method in which the“Bias Power 3” level is increased to compensate for the shortage ofirradiation energy. A setting table of “Bias Power 3” is provided inaccordance with the radius so that controlling is performed. Values oflinear velocity are recorded in the control information area of the diskin advance. When the numerical values are used for interpolation, thetable can be generated. In this method, there is a possibility that theoptimum value of “Bias Power 3” will be displaced if the characteristicof the laser drive circuit varies according to the apparatus. It istherefore necessary to search for the optimum value of bias power in atest write region at the time of insertion of the disk.

In another method to compensate for the shortage of irradiation energycaused by the rise and fall characteristic of the laser drive circuit,as shown in FIG. 11, the peak power level in the multi-pulse chain isset as a level “Peak Power 2” different from the level of the first andlast pulses so that the level “Peak Power 2” cooperates with the level“Bias Power 3” in accordance with the linear velocity in the same manneras in the aforementioned strategy. In this case, the power level of thefirst and last pulses is provided as “Peak Power 1” distinguished from“Peak Power 2”. When “Peak Power 2” and “Bias Power 3” are set, theaverage power level of the multi-pulse chain portion can be controlled.Since the difference between “Peak Power 2” and “Bias Power 3” can beset to be small, the influence of variation in the rise and fallcharacteristic of the laser drive circuit can be reduced. When thelinear velocity becomes further high, the values of “Peak Power 2” and“Bias Power 3” are set to be equal to each other and changed inaccordance with the linear velocity in order to eliminate the influenceof variation in the characteristic. According to this method,information can be recorded accurately when parameters ranging from ahigh velocity to a low velocity are set without any change of thefundamental shape of the write strategy. Also in this case, theaforementioned strategy for changing the positions of the first and lastpulses in accordance with the preamble and following space length s andthe disk's own mark length has an effect particularly on low-velocityrecording.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. An optical disk recording method used for an optical disk having arecording film capable of being changed to an optically different stateby irradiation with an energy beam to thereby record information, saidmethod being provided for recording information as a recording marklength and preceding and following space lengths in said opticallydifferent state by irradiating said recording film with a multi-pulsechain of said energy beam having at least two emission power levels eachhaving an emission time changed in accordance with said optical diskwhile there is relative movement between said energy beam and a surfaceof said recording film of said optical disk, the method comprising thesteps of: recording information on the optical disk with the multi-pulsechain using setting-values; and changing a position and a width of afirst pulse and a last pulse in the multi-pulse chain on the basis of afirst table, a second table and a third table; wherein: thesetting-values concerning the multi-pulse chain for predeterminedrecording velocity are expressed as a sum of a linear term and anonlinear term, and coefficients of the linear term and the nonlinearterm are expressed as integers respectively, the first table hascoefficients of the linear term for the predetermined recording velocityand is designed to specify the position of the first pulse, and thecoefficients in the first table are defined based on recording marklength and preceding space length, the second table has coefficients ofthe linear term and the nonlinear term for the predetermined recordingvelocity and is designed to specify the width of the first pulse, andthe coefficients in the second table are defined based on recording marklength and preceding space length, and the third table has coefficientsof the linear term and the nonlinear term for the predeterminedrecording velocity and is designed to specify the width of the lastpulse, and the coefficients in the third table are defined based onrecording mark length.
 2. An optical disk device comprising: an energybeam generator; a power adjusting unit by which emission power of anenergy beam generated by said energy beam generator can be set to haveat least two predetermined power levels, a holding mechanism for holdingan optical disk having a recording film capable of being changed to anoptically different state by irradiation with said energy beam havingsaid predetermined power levels to thereby record information, a movingunit by which relative movement is provided between said energy beam anda surface of said recording film of said optical disk, and a conversionunit for converting information to be recorded into a power level changeof said energy beam, said optical disk device being provided forrecording information as a recording mark length and preceding andfollowing space lengths in said optically different state by irradiatingsaid recording film with a multi-pulse chain of said energy beam havingsaid power levels each having an emission time changed in accordancewith said optical disk while operating said moving unit, wherein: saidoptical disk device further comprises a storage unit; said storage unitstores setting-values concerning the multi-pulse chain for predeterminedrecording velocity, the setting-values are expressed as a sum of alinear term and a nonlinear term, and coefficients of the linear termand the nonlinear term are expressed as integers respectively, saidstorage unit further includes a first table and a second table forchanging a position and a width of a first pulse in the multi-pulse, anda third table for changing a width of a last pulse in the multi-pulsechain; the first table has coefficients of the linear term for thepredetermined recording velocity and is designed to specify the positionof the first pulse, and the coefficients in the first table are definedbased on recording mark length and preceding space length, the secondtable has coefficients of the linear term and the nonlinear term for thepredetermined recording velocity and is designed to specify the width ofthe first pulse, and the coefficients in the second table are definedbased on recording mark length and preceding space length, the thirdtable has coefficients of the linear term and the nonlinear term for thepredetermined recording velocity and is designed to specify the width ofthe last pulse, and the coefficients in the third table are definedbased on recording mark length, and said power adjusting unit performsemission pulse timing control referring to said first, second and thirdtables.
 3. An optical disk having a recording film capable of beingchanged to an optically different state by irradiation with amulti-pulse chain of an energy beam having at least two emission powerlevels to thereby record information as a recording mark length andpreceding and following space lengths, the optical disk comprising:setting-values concerning the multi-pulse chain for predeterminedrecording velocity, a first table designed to specify a position of afirst pulse of a multi-pulse chain, a second table designed to specifythe width of the first pulse, and a third table designed to specify thewidth of a last pulse of a multi-pulse chain, wherein: thesetting-values are expressed as a sum of a linear term and a nonlinearterm, and coefficients of the linear term and the nonlinear term areexpressed as integers respectively, the first table has coefficients ofthe linear term for the predetermined recording velocity, and thecoefficients in the first table are defined based on recording marklength and preceding space length, the second table has coefficients ofthe linear term and the nonlinear term for the predetermined recordingvelocity, and the coefficients in the second are defined based onrecording mark length and preceding space length, and the third tablehas coefficients of the linear term and the nonlinear term for thepredetermined recording velocity, and the coefficients in the thirdtable are defined based on recording mark length.